This invention relates to building methods and, more particularly, provides a new building method using prefabricated wall panels interconnected by cast-in-situ columns.
The conventional methods of building with reinforced concrete and bricks and mortar infill walls are very labour intensive, primarily because they involve workers from many different trades.
Building methods using prefabricated wall panels and slabs and, sometimes, prefabricated columns are less labour intensive but the existing methods have considerable disadvantages.
In one existing method the wall panels are erected and held together using welded steel brackets. The panels are normally spaced about 20 mm apart and the gap is filled with grouting of non-shrink cement mortar, with or without a sealant on the external surface. Because of the narrow gap, it is difficult to complete the grouting properly. Because temperature changes cause expansion and contraction and wind force causes the building to move, the grouting may crack. Where sealants are used, these may deteriorate over a period of time. Both these effects will lead to ingress of water. Thus, in the long term maintainance costs are much higher than for a conventional reinforced concrete building with bricks and mortar infill walls.
In another method, columns, which may either be pre-cast or cast-in-situ, having panel-receiving grooves on their vertical surfaces are first erected. The wall panels are then lifted and fitted into the grooves and the joints grouted. This method has the disadvantage that the columns being cast first are rigid and in a fixed orientation so that any irregularity in alignment cannot easily be concealed and touch up work is laborious.
Thus, a new method for building using prefabricated wall panels that does not involve the use of grouting between the panels or between the panels and pre-erected columns would be particularly advantageous.
According to the invention, a building is erected using pre-cast wall panels, preferably load-bearing wall panels having a shear key on each vertical edge and starter bars on each horizontal edge, by first erecting the wall panels, and then casting a concrete column around the vertical edges of adjacent or intersecting wall panels using movable formwork made up from a set of standard modules that can be assembled to form different configurations of column for different panel arrangements.
The set of standard modules for assembling the formwork preferably comprises at least four different shaped modules, namely modules for forming straight sections, modules for forming curved sections of various radii and infill modules for forming a corner where two other modules coincide other than in a straight line.
The modules have means by which they can be connected together to form various shapes and sizes of column for joining two, three or four wall panels or for supporting a single wall panel at the end of a wall, such means on the straight and curved section modules preferably being flanges that can be held together by clips or other fastening means that extend rearwardly of the modules on their longitudinal edges. The infill modules preferably are hollow, generally square, tubes but preferably have one rounded corner.
The curved section modules preferably terminate in straight sections so that they can more readily be aligned with adjoining modules.
The moulding surfaces of the modules may, if desired, be shaped to impart decorative features to the cast columns. The pattern of any decorative features can be varied by using differently shaped modules.
The building method of the invention provides a number of advantages over the prior methods, for example,
a) if space allows, the panels can be cast on site, which avoids the cost of delivery to the site,
b) the surfaces of the wall panels can be cast with decorative features, if desired,
c) the wall panels can be cast in any thickness to suit architectural and structural engineering requirements,
d) the surface of the wall panels can be cast in fine concrete so that no plastering or other finishing of the walls is necessary,
e) door, window and other openings can be incorporated into the wall panels in the casting process,
f) the wall panels can be cast with either sleeping or standing formwork,
g) the presence of shear keys and starter bars in the wall panels gives strong interlocking and high building strength after the columns have been cast,
h) various sizes of wall panel can be used in the method, which allows the architect great freedom of design
i) the alignment of the wall panels is easily controlled by seating the wall panels between removable timber markers.
j) any slight out-of-alignment of the wall panels can be easily concealed by the cast-in-situ columns.
k) the cast-in-situ columns prevent any ingress of water.
l) the decorative edge of cast-in-situ columns provides an interesting feature and design to the wall/column intersections.